We have a Lifepo4 and Gel Calcium mixed bank of house batteries on our boat. The Lifepo4 is 660ah and the Gel calcium is 480ah. We limit the output of the main engine alternator, 125A, to 30A by putting its output through a Victron 30A DC DC charger. This is configured so the engine battery is connected to one output of a battery isolation device and our other bow thruster battery is conected to anouther output. The house bank is directly connected to the alternator output, which is also connected to the input of the battery isolation device. The DC DC is set to Lifepo4. The problem is that the DC DC recieves around 13.5v from the alternator but only outputs around 12.1v ? We have a shunt on the Alternator output and I can see around 25A to 35A, which I have verified with a clamp on ammeter on both the input and output of the DC DC charger and it is correct. Our problem is that at 12.1 volts the Lifepo4 battery isn’t receiving enough voltage to charge effectively and the outcome is that after say 12 hours running the engine we only get to about 25% charge. As an aside the DC DC is very warm to the point of being almost too warm so its generating a lot of heat.
